Keep in mind when planting that Cornuta, Mixed Colors is thought of as hardy, so Cornuta, Mixed Colors will tend to go dormant or grow slowly over the winter months.
By our calculations, you should look at sowing Cornuta, Mixed Colors about 90 days before your last frost date.
Ensure that temperatures are mild and all chance of frost has passed before planting out, as Cornuta, Mixed Colors is a hardy plant.